The present invention relates to a burn inhibitor propellant grains having a fluorocarbon binder as one of its constituents.
To prevent burning on certain areas on the surface of a propellant grain, these surfaces are coated with a material which does not readily burn. Inhibitors in the early rocket propellants consisted of strips of plastic cemented to the grain according to a prescribed pattern. Many of the recent rockets use the internal tubular charge in which burning is initiated at the inner surface, progressing outward. These grains must be so inhibited or restricted that no burning on the outer surface, and the ends may also be inhibited. The development of satisfactory inhibiting materials and techniques is considered by many to be one of the greatest problems to overcome in the advancement of rocket technology. In case-bonded propellants, that is, those propellants whose outer surface is bonded directly to the rocket motor casing, only the ends need the inhibiting material. The greatest use of inhibitors is for the cartridge loaded propellants or flares wherein the propellant grain is fully cured and then slipped into the motor casing. The problem of finding materials suitable for inhibiting the extruded and cast fluorocarbon bound propellants is difficult to solve because of plasticizer migration into the grain, incompatibility of the inhibitor and fluorocarbon propellant composition and cracking of the material after curing. The present invention overcomes the above mentioned difficulties.